Distributor vacuum advance valve



Dec. 5, 1967 R. E. CLARK ET AL 3,356,083

DISTRIBUTOR VACUUM ADVANCE VALVE Filed Feb. 1, 1966 1w m4? 5% J W a 0% g #4 a 1 4 J @W Z J H /a a 2 f H 0H4 /0 J J W 4 J 44 5 I If 11 f s A m J my; F a a 0 3 3 5 y E @234 a m a 1/1 j 1 j 1 a w J 1 0M J 1 a w 1 i J spark at idle to fire at United States Patent 0 3,356,083 DISTRIBUTOR VACUUM ADVANCE VALVE Robert E. Clark and Jorma 0. Sarto, Orchard Lake, Mich., assignors to Chrysler Corporation, Highland Park, Mich., a corporation of Delaware Filed Feb. 1, 1966, Ser. No. 524,230 9 Claims. (Cl. 123117) This invention relates to improvements in carburetion for a piston type automotive internal combustion engine and in particular to simple and improved means responsive to the pressure in the fuel-air inlet induction conduit or manifold for advancing the engine ignition spark distributor during deceleration or coasting and for retarding the ignition distributor during normal engine idling so as to achieve improved combustion and to minimize the exhausting of unburned hydrocarbons. An example of the structure with which the present invention is concerned is illustrated in copending application of Jorma O. Sarto, Ser. No. 318,285, filed Oct. 23, 1963, now Patent No. 3,252,451, to which reference is hereby made for details of structure and operation. The present invention is concerned with improvements in the pressure actuated valve means described in the aforesaid application.

It has been common heretofore to advance and retard the ignition distributor in accordance with engine speed and manifold pressure. For example it has been customary during engine idling to advance the distributor to fire when the engine piston is approximately 10 of crank shaft rotation in advance of its topmost or dead-center position and thereafter to progressively advance the distributor with increasing engine speed. Operation under such conditions results in optimum fuel economy but requires a fuel-air ratio during engine idling appreciably greater than the stoichiometric ratio of approximately .067 pound of fuel per pound of air which supplies the minimum air required for complete combustion of the fuel. Furthermore, during engine coasting above approximately 25 miles per hour in high gear, the inlet manifold vacuum rises to between 22 and 25 inches of mercury (i.e., the absolute pressure falls) at which low pressures under conventional operating conditions, failure of engine combustion usually occurs and large amounts of unburned hydrocarbons are exhausted to the atmosphere. I

It has been found that if the ignition spark distributor is retarded to fire when the piston is approximately 5 to degrees of crankshaft rotation beyond its top or dead center position, the engine can be idled with an appreciably leaner fuel-air mixture approximating the stoichiometric ratio, provided that the fuel consumption is increased slightly above the customary idling value for optimum fuel economy. In consequence, the exhausting of unburned hydrocarbons is materially reduced. For example, an engine that would customarily idle at a fuel-air ratio of .087 pound of fuel per pound of air and an air consumption of 35 pounds per hour can be operated to effect almost complete fuel combustion at a fuel-air ratio of 0.70 pound of fuel per pound of air and an air consumption of 54 pounds per hour merely by retarding the of crankshaft rotation after the dead-center position, rather than at the customary 10 in advance of the dead-center position.

In addition, by retarding the spark and increasing the fuel consumption as above, the engine can be operated without combustion failure at a manifold vacuum in excess of 22 inches of mercury. Accordingly slow speed coasting in high gear, as for example in city traflic with the throttle closed to the idle condition, does not appreciably increase the unburned hydrocarbon content of the exhaust. At higher coasting speeds, as for example in excess of approximately 25 miles per hour in high gear and at the idle throttle position, it is preferred to advance the ignition spark as the manifold vacuum increases, in order to obtain substantially complete combustion of the fuel.

In order to accomplish engine operation in accordance with the foregoing, the carburetor is designed to supply idle fuel at an accelerated rate with respect to customary engine idling heretofore, but at an appreciably leaner fuel-air mixture approximating the stoichiometric ratio. Pressure actuated means responsive to manifold intake pressure is operatively connected with the ignition spark distributor mechanism to retard the spark during idling and low speed coasting and to advance the spark rapidly when the coasting speeds exceed a predetermined value, as for example 25 miles per hour.

The pressure actuated means is biased to retard the spark during engine idling, so as to fire 5 to 15 beyond the top center position as aforesaid, and is normally connected in accordance with customary practice with the intake manifold adjacent the throttle valve in order to advance the spark with increasing fuel consumption, as is conventional. A second connection between the pressure actuated means and intake manifold at a location downstream of the throttle valve is normally closed by a double actuated valve at its usual operating or at speeds greater than approximately twenty-five miles per hour while the throttle is at 35 before the top center position.

An important object of the present invention is to pro vide an improved double and closing said cutomary first named connection so as to advance the spark during high speed coasting.

Another object is to provide a pressure actuated valve that can be mass produced economically for the highly competitive automotive industry, yet which is efiicient in or closes the associated lowing description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

FIGURE 1 is a schematic view showing a carburetor in section and embodying an ignition spark control mechanism operatively connected with an ignition spark distributor.

FIGURE 2 is an enlarged longitudinal mid-sectional view through the valve mechanism responsive to the induction pressure.

FIGURE 3 is a fragmentary enlarged view of the valve in FIGURE 2.

FIGURE 4 is a view similar to FIGURE 3, illustrating a modification of the valve.

It is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Referring to FIGURES 1 and 2, a particular embodh ment of the present invention is illustrated by way of example with a carburetor having a typical air inlet induction manifold or conduit 11, choke valve 12, and throttle valve 13. This structure may be conventional and will also embody the necessary idle fuel duct 16a and primary fuel duct 10b for admitting fuel to the induction conduit 11 during idle and load conditions of the engine for which the carburetor is provided.

Also associated with the engine is a conventional spark distributor 14 operatively connected with a distributor advancing and retarding mechanism, which includes the customary flyweight type speed responsive governor mechanism 14a for advancing the ignition with increasing speed and also includes a pressure responsive means indicated generally by the numeral 15 and comprising a pressure chamber 16 defined in part by a movable wall or flexible diaphragm 17. The latter is connected with a reciprocal plunger 18 which in turn is operatively connected with the distributor 14 to advance or retard the timing of the engine spark or firing in cooperation with the governor mechanism 14a in accordance with leftward or rightward movement respectively of diaphragm 17 and plunger 18 in FIGURE 1.

A biasing spring 19 normally maintains the distributor in a retarded condition to cause spark or firing in the cylinder concerned at between approximately 5 to 15 of crank shaft rotation after the engine piston has passed its top or dead-center position when the engine is idling normally. In this regard, for operation with the ignition spark retarded as aforesaid, the carburetor is designed to supply fuel at an accelerated rate with respect to customary engine idling but at an appreciably leaner fuel-air mixture approximately the stoichiomctric ratio of about .070 pound of fuel per pound of air. During engine idling and also during coasting of the engine, the throttle valve 13 is substantially closed and the pressure in conduit 11 downstream of throttle valve 13 is low. When the engine is coasting at speeds greater than 25 miles per hour, the vacuum downstream of throttle valve rise to between 22 and 25 inches of mercury.

In order to avance the ignition spark in response to an increased vacuum downstream of throttle valve 13 during deceleration or coasting in gear, a valve is provided having a tubular housing 29 with an intermediate inwardly directed annular extension 21 around a port or opening 22. The extension 21 terminates in an annular valve seat 23 coaxial with opening 22 and tubular housing 20. An internally threaded portion of the housing screws on an externally threaded portion 24 of the housing 25 of a pressure actuated device partitioned into two chambers 26 and 27 by means of a movable wall or flexible diaphragm 28. The latter is secured around its periphery to the housing 25 and is secured centrally in supporting relation to one end of a reciprocal shaft 29 to actuate the latter in accordance with the pressure differential across diaphragm 28.

The shaft or plunger 29 extends coaxially into housing 20 and through opening 22 and is secured at its right end to a suitable valve member 30 comprising a rigid annular disc type end cap 50 spacing annular sealing washers or elements 51 and 52. The cap 50 maybe of metal or other form sustaining material suitable to comprise a backing for the flexible washers 51 and 52, which latter may be of somewhat yieldable or resiliently deformable rubber- 13 will frequently like material adapted to seat in sealing contact at their associated valve seats as described below. The washers 51 and 52 may be secured to or carried by the cap or may be loosely piloted within the tubular housing 20. In the present instance, the washer 51 is loosely confined between valve seat 23 and disc 50 and is free to rest on the bottom of the adjacent interior wall of housing 20. For this reason, the annular clearance between washer 51 and the interior of housing 20 is maintained comparatively small, but is adequate to permit unrestricted passage of gases during operation of the valve, as described below. The washer 52 is confined within an annular coaxial groove in the base of cap 59.

In FIGURE 2, the cap 50 has a central bore 53 extending partially therethrough from the left in FIGURE 2 and dimensioned to receive the reduced right end of shaft 29 loosely therein. The right end of bore 53 is closed by the base of cap 50. The reduced right end of shaft 29 is secured to cap 50 by means of a diametrical pin 54 tightly confined within mating radial holes in cap 50 so as to seal the latter holes closed. The pin 54 also extends diametrically through an hourglass shaped hole 56 in the reduced right end of shaft 29 and comprising two radially diverging conical parts coaxial with a common diameter of shaft 29 and cap 50. The two conical parts of hole 56 communicate with each other adjacent the longitudinal axis of shaft 29 to provide an annular pivot region closely confining pin 54 to prevent axial play between plunger 29 and cap 5%), yet to allow limited universal pivoting of the latter by reason of the clearance provided by the hourglass hole 56 and the oversize bore 53 around shaft 29.

A tubular spring retainer 31 arranged coaxially around plunger 29 screws into an internally threaded portion of extension 24 and provides an abutment for one end of a spring 32 coiled around shaft 29 and seated at its other end against a rigid portion of diaphragm 28 to urge the latter leftward in FIGURE 2, thereby to maintain valve 30 in its closed position with sealing element 51 seated against seat 23. Suitable annular seals 33 and 34 are provided between extension 24 and retainer 31 and housing 20 respectively to maintain a leak-proof enclosure for chamber 27.

The extension 21 in cooperation with valve 30 serves to partition housing 20 into two chambers 35 and 36, the chamber 35 being in continuous unrestricted communication with chamber 27 via central bore 37 in retainer 31 through which shaft 29 extends. The chambers 35 and 36 are in communication with each other when valve 30 is shifted rightward to its open position.

Chamber 27 is also maintained in unrestricted communication with conduit 11 by means of conduit 33 which opens into conduit 11 at port 39 downstream of throttle valve 13, such that when the latter is opened from its idle position shown in FIGURE l, the increased pressure at port 39 will be too great to cause rightward opening of valve 30, as described below. Chamber 26 is maintained in unrestricted communication with atmospheric air by port 40. Chamber 36 is maintained in unrestricted communication with chamber 16 by meansof conduit 42, whereby diaphragm 17 is actuated in response to the pressure in chamber 36.

As illustrated in FIGURE 2, the right end of chamber 36 is closed by means of a tapered screw threaded fitting 43 having a coaxial inwardly directed annular valve seat 43!). A restricted bleed port 44 opens into induction conduit 11 at a location adjacent throttle valve 13 when the latter is in its closed or idle position and is in restricted communication with chamber 36 by means of conduit 42b which extends coaxially through fitting 43 within the confines of valve seat 43!) and is restricted adjacent the latter at 42a. The valve seat 43b is adapted to be engaged by sealing element 52 when valve 30 moves rightward to its open position, thereby to close the connection between port 44 and chamber 36 and prevent dilution of the fuel-air mixture downstream of port 39. Similarly,

port 44, which is ordinarily connected with chamber 16 via ducts 42b and 42 and which serves as the conventional distributor vacuum advance port for engine operation under cruising conditions when throttle valve 13 is partially open, is blocked from chamber 16 when valve 30 is at its rightward or open position against seat 43b.

The vacuum advance port 44 is conventionally employed in cooperation with the speed responsive mechanism 14a for advancing the ignition spark with increasing speed until at about 30 m.p.h., the ignition spark or firing will occur at a predetermined angle of crankshaft rotation amounting to about 35 in advance of the top center position of the engine piston involved. Combustion in the engine cylinder will thus occur when the engine piston is adjacent its topmost position whereat optimum compression of the fuel-air mixture in the engine cylinder occurs, i.e., when the density of the fuel-air mixture is a maximum. Most of the fuel will be burned before being scavenged from the cylinder and optimum fuel economy will be achieved during cruising conditions. By virtue of the structure described, the cap 50 moves to the left or right with plunger 29 upon corresponding actuation of diaphragm 28, so as to seat washer 51 or 52 against annular valve seat 23 or 43b respectively. The bore 53 in cap 50 provides sufficient clearance for the reduced right end of plunger 29, so that the axially pposed end faces of cap 50 will remain perpendicular to the axis of housing 20 and cause the washers 51 and 52 to seat flush against the respective valve seats 23 and 43b. Positive fluid sealing contact of valve 30 at the seats 23 and 43b is thus assured regardless of cocking of plunger 29 out of coaxial alignment. In the latter regard, the diaphragm 28 is arranged symmetrically With respect sufiiciently rigid to hold the latter in the desired coaxial alignment. However, in consequence of the continuous pressure for cost reduction and unavoidable production tolerances in the diaphragm 28, spring 32, and associated elements, the plunger 29 cocks out of its desired coaxial alignment in certain installations, especially during the initial stages of the pressure actuated movement of diaphragm 28 between the closed and open positions of valve 30. The pivotal mounting of the valve 30 on one end of shaft 29, which has its other end secured to diaphragm 28 as described, achieves a particularly effective and economical construction.

' During normal-idling conditions, spring 32 will maintain valve 30 in its closed position in opposition to the vacuum induced force on diaphragm 28 caused by the low pressure downstream of throttle valve 13. The pressure in chamber 36, after equilibrium is established through restricted port 44, will be substantially atmospheric and will cooperate with spring 19 to urge the distributor 14 to its most retarded position, thereby to cause engine firing between to of crankshaft rotation beyond the top center position of the engine piston involved. During engine coasting or deceleration at slow speeds, the governor mechanism 14a will have no appreciable effect. As the coasting speed increases, the vacuum downstream of throt-tle valve 13 will gradually increase and also the governor mechanism will be increasingly effective to reduce the spark retardation. At a predetermined vacuum, as for example inches of mercury which corresponds approximately to a coasting speed of 30 miles per hour, the low pressure at port 39 transmitted to chamber 27 will cause rightward shifting of diaphragm 28 and opening of valve 30 against the tension of spring 32.

It is to be noted that immediately upon opening of valve 30, the comparatively high pressure in chamber 36, acting ondisk valve 30 to urge the latter closed, is dissipated through port 37 and conduit 38. In consequence, valve 30 operates somewhat as a poppet valve, such that after its initial opening, valve 30 will rapidly move to its fully open position. Small variations in manifold pressure will not cause it to close again until the coasting speed numbered. Instead of the decreases to approximately 20 miles per hour. When valv 30 is open, the low pressure in chamber 36 will be trans mitted via conduit 42 to chamber 16 to cause leftwan movement of diaphragm 17 against the tension of spring 19, thereby in cooperation with the governor mechanisn 14a to advance the distributor 14 to cause firing at ap proximately 35 of crankshaft rotation before the aforesaid top center position, i.e., at approximately the same angular position of the crankshaft as would result during conventional cruising. Thus optimum combustion will occur during the period of maximum density of the fuelair mixture, with a minimum discharge of unburned hydrocarbons to the atmosphere.

As the valve 30 is seated or unseated with respect to one of the annular valve seats 23 or 4311, its pivotal freedom tends to cause momentary chattering and objectionable valve noise. The aforesaid poppet action of valve 30 tends to reduce these objections. This action is enhanced by means of the restriction 42a in conduit 42b. During coasting when the pressure upstream of throttle valve 13 and correspondingly the pressure conducted to chambers 36 and 16 via port 44 and conduit 42b and 42 are comparatively high and when the pressure in chamber 27 becomes suificiently low to shift valve 30 rightward to its open position, the initial opening of valve 30 enables a rush of the high pressure gases from chamber 36 into chamber 27, tending to increase the pressure in the latter chamber and return valve 30 to its leftward closed position with resulting valve noise. By virtue of restrictions 42a and 44 in series, the flow of such gases into chamber 36 via port 44 is retarded. The high pressure in chamber 36 opposing rightward shifting of valve 30 is rapidly dissipated via duct 38 and valve 30 moves positively rightward to its open position seated against valve seat 43b.

By maintaining restriction 42:: very close to valve seat 43b and chamber 36, the volume of gases to be exhausted from the latter chamber, so as to reduce the pressure therein and effect the poppet type valve action, is reduced to a minimum. Also, by maintaining the diameter of valve seat 43b comparatively small with respect to the diameter of valve seat 23 and especially with respect to the diameter of diaphragm 28, the effect of losing the high pressure within the confines of seat 43b upon leftward closing movement of valve 30 from seat 43b is rendered inconsequential. Upon the continued leftward closing movement of valve 30 into proximity with seat 23, the high pressure in chamber 36 will be restored, thereby to positively close valve 30 and maintain the latter closed regardless of minor pressure variations in chamber 27. The pressure conditions for actuating valve 30 are thus rendered critical and sharply defined and the noise inherent in the use of the pivotal valve 30 is reduced to a minimum.

Also in the above regard, port 44 is partially covered and restricted by the edge of valve 13 in the idle position shown, so as to afford optimum restriction in cooperation with restriction 42a during high speed coasting conditions when diaphragm 28 operates to shift valve 30 rightward ,to the spark advancing position. During open throttle conditions when diaphragm 28 and valve 30 are at their leftward position, port 44 will be downstream of the upper edge of valve 13 and unobstructed thereby, so as to serve its conventional function of advancing the ignition spark with increasing engine speed.

FIGURE 4 illustrates a modification of the pivotal valve wherein most of the parts are the same in structure and operation as described above and are correspondingly integral cap 50, a two-piece cap is employed comprising an annular disc a and a closure cap 50b. The latter seats in fluid sealing arrangement with in the enlarged right end opening of the bore 53a in disc 50a, so as to close the same and provide a pilot for washer 52. The reduced end of plunger 29 comprises a pin 29a secured within a mating opening in plunger 29 and extending with clearance coaxially through bore 53a and terminating in an enlarged head 2% within cap 50b. Disc 5041 is confined loosely between the end of plunger 29 and head 29b to enable its limited pivotal adjustment as required to accommodate cocking of plunger 29 and to maintain washer 51 or 52 seated flush against the associated valve seat 23 or 4312 upon closing or opening of valve 30.

We claim:

1. In combination, a pair of axially spaced valve seats defining a corresponding pair of ports, an axially reciprocable valve plunger extending axially through one of said ports into the space between said valve seats, valve means in said space adapted to seat selectively at either of said valve seats to close the corresponding port, and means for mounting said valve means on said plunger for limited universal pivoting thereon to accommodate cocking of said plunger relative to said valve means when the latter is seated at either of said valve seats including an axial hole in said valve means oversize with respect to said plunger and having the latter extending loosely therein and also including interengaging means carried by said plunger and valve means for selectively shifting the latter to seat at one or the other of said valve seats upon axial shifting of said plunger in one direction of the opposite.

2. In the combination according to claim 1, said means for mounting said valve means on said plunger comprising an hourglass shaped pin hole extending diametrically through said plunger, and a pin extending diametrically through said hourglass shaped pin hole and into mating diametrically opposed pin holes in said valve means, said pin frictionally engaging said valve means within the latter pin holes to seal the same closed and to secure said pin to said valve means, said pin also being closely confined pivotally by said plunger at the restricted region of said hourglass shaped pin hole to limit axial movement of said plunger relative to said pin while enabling said limited universal pivotal movement of said valve means to the extent of the pivotal movement of said pin within said hourglass shaped pin hole.

3. In the combination according to claim 1, said one port being defined by one of said valve seats and the other of said ports being defined by the other of said valve seats, and means associated with said other port for normally restricting the flow of fluid therethrough into the space between said valve seats.

4. In the combination according to claim 1, housing means defining a chamber and said valve seats, said valve means cooperating with one valve seat defining said one port to partition said chamber into two parts when said valve means is seated at said one valve seat, said one port connecting said two chamber parts when said valve means is unseated from said one valve seat, said housing means including a pressure actuated flexible diaphragm spaced axially from said one port and defining a wall portion of one of said chamber parts, said space between said valve seats comprising the other chamber part, the other of said ports opening from said other chamber part, means securing said plunger to said diaphragm for reciprocation upon actuation of the latter and for supporting said plunger generally coaxially within said one port.

5. In the combination according to claim 4, said means for mounting said valve means on said plunger including a pin secured to said valve means and extending generally diametrically through a portion of said plunger within said other chamber part, an annular pivot edge of said plunger extending closely around the periphery of said pin at the region of its passage through said plunger for pivotally engaging said pin, and also including a recess in said plunger providing clearance for said pin to enable the latters limited universal pivotal movement on a portion of said pivot edge.

6. In the combination according to claim 4, pressure actuated distributor timing means connected with said other chamber part, a carburetor for an automotive interial combustion engine and having a fuel-air induction conduit, a butterfly type throttle valve in said induction conduit, a conduit connecting said one chamber part with said induction conduit at a location downstream of said throttle valve when the latter is at an idle position, a distributor control port opening into said induction conduit and disposed adjacent an edge of said throttle valve when the latter is at its idle position, said edge being movable to a location upstream of said control port upon opening of said throttle valve from said idle position, a second conduit connecting said control port with said other port and thus with said other chamber part, thereby to establish communication between said control port and said pressure actuated distributor timing means to actuate the latter when said valve means is seated at said one valve seat, means for restricting the flow of fluid through said second conduit comprising a restriction therein immediately adjacent the opening thereof into said other chamber part, and means yieldingly urging axial displacement of said plunger in the direction to seat said valve means at said one valve seat.

7. In the combination according to claim 6, said edge of said butterfly type throttle valve adjacent said control port partially restricting the opening of the latter into said induction conduit when said throttle valve is at said idle position.

8. In the combination according to claim 6, said means for mounting said valve means on said plunger including a pin secured to said valve means and extending generally diametrically through a portion of said plunger within said other chamber part, an annular pivot edge of said plunger extending closely around the periphery of said pin at the region of its passage through said plunger for pivotally engaging said pin, and also including a recess in said plunger providing clearance for said pin to enable the latters limited universal pivotal movement on a portion of said pivot edge.

9. In the combination according to claim 4, pressure actuated distributor timing means connected with said other chamber part, a carburetor for an automotive internal combustion engine and having a fuel-air induction conduit, a butterfly type throttle valve in said induction conduit, a conduit connecting said one chamber part with said induction conduit at a location downstream of said throttle valve when the latter is at an idle position, a distributor control port opening into said induction conduit and disposed adjacent an edge of said throttle valve when the latter is at its idle position, said edge being movable to a location upstream of said control port upon opening of said throttle valve from said idle position, a second conduit connecting said control port with said other port and thus with said other chamber part, thereby to establish communication between said control port and said pressure actuated distributor timing means to actuate the latter when said valve means is seated at said one valve seat, and means yieldingly urging axial displacement of said plunger in the direction to seat said valve means at said one valve seat.

References Cited UNITED STATES PATENTS RALPH D. BLAKESLEE, Primary Examiner.

Disclaimer 3,356,083.R0bert E. Ularlc, and Jorma. O. Sarto, Orchard Lake, Mich. DIS- TRIBUTOR VACUUM ADVANCE VALVE. Patent dated Dec. 5, 1967. Disclaimer filed Apr. 28, 1969, by the inventors; the assignee, Chrysler Corporation, consenting. Hereby enter this disclaimer to claims 2 through 9 of said patent.

[Ofiicial Gazette July 8, 1.969.] 

1. IN COMBINATION, A PAIR OF AXIALLY SPACED VALVE SEATS DEFINING A CORRESPONDING PAIR OF PORTS, AN AXIALLY RECIPROCABLE VALVE PLUNGER EXTENDING AXIALLY THROUGH ONE OF SAID PORTS INTO THE SPACE BETWEEN SAID VALVE SEATS, VALVE MEANS IN SAID SPACE ADAPTED TO SEAT SELECTIVELY AT EITHER OF SAID VALVE SEATS TO CLOSE THE CORRESPONDING PORT, AND MEANS FOR MOUNTING SAID VALVE MEANS ON SAID PLUNGER FOR LIMITED UNIVERSAL PIVOTING THEREON TO ACCOMMODATE COCKING OF SAID PLUNGER RELATIVE TO SAID VALVE MEANS THE LATTER IS SEATED AT EITHER OF SAID VALVE SEATS INCLUDING AN AXIAL HOLE IN SAID VALVE MEANS OVERSIZE WITH RESPECT TO SAID 